It's been occurring to me that MovableType is slowing down. The problem is that it's getting slower and slower with every post, since every archive page needs to be rebuilt with the dynamic left items (recent posts, category post #, etc). The more posts, the more pages to rebuild. Over and over. Here's what I'm thinking of doing to speed everything up, and never rebuild archives again.
[haven't done this yet]
The only info in the archives that's ever changing is the left-hand bar. It would be better to rebuild one page with that info, and have it included in all the archived pages and categories.
Remove all the dynamic items from the left in all the templates. Create a new template that just includes the dynamic items that used to be in the left side bar. Now using PHP, include the new "left template" into all of the old templates where the left side info used to be.
When rebuilding, only rebuild the new "left template" and the index templates. All the archive pages will get the new content (recent posts, category post #, etc) from the left template that they're all inserting into themselves.
[/haven't done this yet]
Make sense? Simple as pie. In the next day or so I'll see if i can't get it to work.